Jeroen van Oijen (C) Bart van Ooverbeeke
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A group of researchers at Eindhoven University of Technology (TU/e) think there is still a future for the combustion engine. The secret lies in the noble gas argon in combination with green hydrogen. With the Argon Power Cycle (APC), the emission of CO2 and nitrogen oxide can be brought down to a minimum, says researcher at the Faculty of Mechanical Engineering Jeroen van Oijen in an interview on the TU/e website. Consideration should be given to large installations in particular. This makes the APC technology unsuitable for cars or trucks, but it could qualify for use in ships or industry.

“We at TU/e firmly believe that we can innovate the internal combustion engine in such a way that it can continue to be used throughout the 21st century,” says van Oijen. To achieve this, TU/e is researching a number of environmentally friendly upgrades for this engine.

“One of the things I’m working on is the APC engine. APC is a revolutionary technology that uses argon as its operating fluid instead of air. Combine that with hydrogen as a fuel, and you have a highly efficient machine that is not only emission-free, but can also help store green energy from sun and wind.”

Further development of the diesel engine

One of the main challenges is that argon tends to heat up very quickly when compressed. The mixture then combusts before you reach the optimum pressure level, to the detriment of the engine’s efficiency. Consequently, new techniques are required to control the combustion process in an argon engine.

This image has an empty alt attribute; its file name is APCscheme-upd-678x564.jpg
Schematic representation of the Argon Power Cycle using hydrogen as a fuel

Van Oijen: “We want to explore three possible solutions in the research project. The first one seems to be the most promising, because it is similar to the method we already use in diesel engines. In this method, the hydrogen is introduced only after the argon and oxygen have been fully compressed. This prevents premature combustion, although there are still some problems to iron out. For one thing, it is proving difficult to inject hydrogen into a compressed gas given how extremely light it is.”

“A second alternative fixes this problem by injecting hydrogen and argon when the pressure level is still low, and adding oxygen at a later stage, when the pressure level is high. The problem here is that this has never been tried before, and that oxygen at high pressures tends to react with the metal of the injector, leading to corrosion.”

“Lastly, we want to look at the possibility of injecting both hydrogen and oxygen at a later stage in the cycle. The challenge here is to coordinate the injection of the two gases to ensure that both gases can find each other and react at the right time.”

Capturing natural gas and CO2

From a climatic viewpoint, it would be less than ideal, but the argon engine might also work with natural gas or biofuels. “Then it would no longer be carbon-free, but the beauty of our setup is that it is self-contained. That makes it much easier and cheaper to capture CO2 emissions. We can then use that as a raw material for the chemical industry. In order to filter out the CO2, we use an advanced membrane that has only a limited effect on the overall efficiency of the system.”

The key question with this type of technology is always, of course, when can it actually be put into practice. There is still plenty of work to be done when it comes to the argon engine. Yet there is already work being done with companies that are capable of getting this off the ground. Among them are the American Noble Thermodynamics and Winterthur Gas & Diesel.

Other projects that TU/e is working on can be found here.